Permaculture questions are being answered throughout the month of May by our expert authors. Submit your questions here  and read on to see what Eric Toensmeier, author of Paradise Lot , Perennial Vegetables  and co-author of Edible Forest Gardens , has to say about invasive grasses and the best plants for shady spots.
Review previous posts from the “Permaculture Q&A” series here:Ben Falk Talks Nutrient Cycling  Toby Hemenway on Soil and Natural Patterns 
Casey from Idaho asks:
Grass takes over my garden beds each spring. I appreciate the ground-cover function, but it out-competes my preferred annuals and perennial producers. And I trust that the problem is the solution, but I can’t see the solution in a permaculture context. How do I bolster the productive cultures when grass is so persistent and aggressive?
Eric Toensmeier: Hi Casey, we have found there is really no middle ground with aggressive lawn grasses in our perennial plantings. You can have trees and larger shrubs with grass beneath them and they will be pretty happy as long as the grass is routinely cut or grazed. But if you want to get into smaller shrubs or perennials our experience is that you really want to nuke the grass.
In our previous garden we had some beds where grasses crept back in and we ended up having to pull out the desirable perennials, sheet mulch the entire bed again thoroughly, and replant our perennials. After that we made sure to keep a mulched perimeter around our beds so that grass could not creep in. You could try rhizome barriers as well, like installing edging maybe 8 to 10 inches deep (depending on what kind of grass you have).
In another situation we had set up long thin mulched beds with long thin grass pathways between them. This really maximized surface area for the grass to get back into the beds and gave us a huge amount of weeding to do. Note that there are some grasses like some of the fescue’s which are not at all aggressive and make very fine path grasses. In our present garden we thoroughly sheet mulched the lawn (such as it was) in the beginning and have really not had any trouble to speak of with grasses returning.
The other approach is something I’ve seen in a food forest in Mexico. They use African weeder geese at a rate of 10 per acre to thoroughly eat down all of the grass until it is completely suppressed. Then they plant a lot of herbaceous species, and reduce the geese to two per acre. This particular breed of geese, raised and taught that grass is food, eat almost nothing but grass and clover, leaving almost all of the herbaceous crop species alone (with a few exceptions). If you are able to have geese in your garden, this seems like a great way to have happy geese and keep the grass under control.
Killian from California asks:
I’m designing a small, very shaded backyard garden in the Seattle area with Homeowner’s Association limitations. I am not a fan of raised beds unless needed (least change), but am thinking of using them throughout this design to alleviate drainage issues, including planting a number of dwarf fruit and nut trees in them. Thoughts?
Eric Toensmeier: Hi Killian, the first thing you’ll have to deal with is your shade problem. There are very few fruits and even less nuts that grow in full shade in your climates. Currants, evergreen huckleberry, mahonia (sour!), and thimbleberry are among your full-shade fruit options. Can you do anything to increase the amount of sun, like take down some trees or trim branches off your neighbor’s trees that come over your property line? Once you get into partial shade there are a lot more options. Good fruits for partial shade include medlar, quince, pawpaw, super-hardy kiwifruit, currants, gooseberries, and raspberries. Hazelnuts are probably your best option for nuts in partial shade.
If you have drainage problems, you could grow some things that don’t mind wet feet, like elderberries, blueberries, saskatoons, aronia, and quinces. I recently saw a very nice raised berm system at East Hill Tree Farm in Vermont using the hugelkultur system. Hugelkultur involves partially rotten logs and branches to form the base of the berm, packed with soil and compost materials. They mulch and plant right into it even the first year. This is probably quicker to establish then fancy raised beds if you have access to the raw materials. Certainly regular old raised beds should work fine, but fruits and nuts are big plants and would require fairly big beds. Hugelkultur is unlikely to be loved by your HOA, but sometimes they ignore backyards. Don’t negelect the steath edible landscape in the front yard, featuring lovely ornamentals that happen to be edible. See Lee Reich’s Landscaping with Fruit for some ideas.
With all that said, here in our garden in Massachusetts we have been able to grow some food in full shade and an awful lot in partial shade. The areas which were poorly drained due to clay (though perhaps not nearly as badly as yours), we were able to improve using a broad fork and increasing organic matter. Check out this video for a tour of a corner of my garden that includes four perennial vegetables perfect for shady spots.